Orthogonal frequency division multiple access (OFDMA) communications use an orthogonal frequency-division multiplexing (OFDM) digital modulation scheme to deliver information across broadband networks. OFDMA is particularly suitable for delivering information across wireless networks.
OFDMA communications may use frequency diversity permutation to enhance the channel reliability by increasing reliability for low signal-to-noise ratio (SNR) communications and/or high-speed mobile stations (MSs). Furthermore, different frequency diversity permutation sequences may be used for different cells in order to reduce the inter-cell interference.
There are many existing permutation methods, e.g., S-Random, full random, and bit reversal. S-Random sequences typically have large frequency diversity gains; however, S-Random sequences of different lengths need to be searched out and stored into table, which will complicate hardware implementation. While full random sequences may be easily implemented, they typically do not achieve a desired diversity gain. Bit reversal is a fixed sequence that can not be used for inner permutation to avoid the inter-cell interference mentioned above.